A New Instrument To Remotely Monitor Rock Mass Deformation

Abstract

A new system for precise monitoring of surface and underground deformations in rock mass surrounding a mining operation has been developed and successfully deployed by CSIRO Exploration and Mining since 1993. The new system is based on a borehole strainmeter, which has the sensitivity to enable measurements remote (for example at distances of 1-5 km) from the mining operation, and long term stability to provide accurate measurements over periods of years. Strainmeters traditionally used for deformation measurement have neither the long-term stability nor the high sensitivity to perform measurements in these applications. This paper describes the new precision borehole strain monitoring system (GTS) currently deployed by CSIRO Exploration and Mining, which has the potential to solve these new issues in rock mass deformation monitoring. This technology was originally developed for use in hard rock mines (Gladwin 1977) and refined considerably for earthquake research (Gladwin et al. 1994, Gwyther et al., 1992). A case study of the use of the GTS in monitoring longwall coal mining over the period 1993-1999 is presented. Accurate measurement of rock mass response during the mining of massive underground ore-bodies is essential as mines become larger and deeper. The CSIRO GTS system is immediately applicable in circumstances such as: provision of quantitative data for optimal pit slope design and engineering; measurement of the stability of deep pit slopes, monitoring the long term integrity of shafts, large scale underground infrastructure and surface infrastructure, and long term measurements of deformation or rock mass creep following the mining process to provide data for environmental management.